This invention relates generally to the field of video processing. More particularly the invention relates to the field of playing a DVD video in reverse.
In the field of video processing, a series of images or frames of video information are displayed in order so as to create a moving image. One common standard for conveying this video information is known as the MPEG standard. While the display of the video images is relatively straightforward when the images are decoded and displayed in the forward direction, displaying the images in the reverse direction has proven to be entirely more difficult. In fact, even though some video players such as the DVD player have been in existence for some time, a system for displaying a continuous reverse image has not successfully been employed.
The underlying problem that creates these difficulties is the way that a video is encoded in the first place. For example, in MPEG, a first video frame is entirely encoded. Succeeding frames are not entirely encoded. Rather, only the changes from the preceding frame are encoded. This conserves the amount of processing time required to decode an image, because the existing information from the first frame can be reused. This process is repeated every few frames such that after a few frames another frame is once again entirely encoded. The process is then carried on again based on this new reference frame.
Consequently, the data that is required to decipher the image for a frame is often cumulative over several frames. While this cumulative information is easily gathered when the video is played in the forward direction, it is not easily gathered when the video is played in reverse.
Other attempts to create a reverse playback video sequence have had various drawbacks. The first drawback is the delay involved in creating a reverse image. Namely, the delay between the user initiating a reverse mode and the actual reverse video being played has been undesirably long. It would be beneficial for a user to be able to initiate a reverse playback mode and for the system to quickly begin the reverse playback. However, with conventional systems, the delay involved to create the reverse image does not satisfy this need. Furthermore, the reverse images displayed are often choppy, such that there is not a seamless reverse playback in such systems. A further drawback of some attempts has been that once the reverse sequence has been initiated, it only plays at xc2xd of normal speed. It would be preferred if the system had the ability to play at normal speed (or faster) but in reverse.
The drawbacks noted above have apparently been caused by attempts by others to recreate the sequence of forward images and store them for reverse play. This takes a great deal of memory to store the video images. Since not all of the video images can be stored in the limited memory of most conventional DVD players, the speed of the reverse playback in these players has to be slowed down to accommodate the creation of additional frames of data as space for storing the new frames becomes available after already played frames are discarded.
Another drawback in video systems has been the lack of a compression system that permits the storage of sufficient information about an image with less memory than that required for the full image. It would be desirable to have a system that allows a video to be played in reverse while not requiring all of the memory for a display of the full image.
The present invention provides a system to overcome these disadvantages and satisfy the needs highlighted by other designs.
In one embodiment of the invention, a system for playing a video in reverse generates frames of a video, scales these frames, stores the scaled frames in memory; and plays the scaled frames in reverse. A decimation algorithm can be used to accomplish the scaling feature of the invention. Furthermore, the scaling of chroma and luma components for a frame can be accomplished independently of one another so as to accomplish the scaling. Reference frames from preceding video object units can be utilized to accomplish the generation of frames for a frame of a present video object unit. The invention is advantageous in that it permits a normal speed reverse playback of a video, rather than the slower playback required by conventional designs. It also can permit a faster generation of the frames for reverse playback. Similarly, it can prevent the choppy playback that occurs with some conventional designs that can not generate frames quickly enough resulting in a delay between succeeding frames in a reverse playback.
In another embodiment of the invention, a video is played in reverse by utilizing information from prior video object units to generate video frames for playback in the current video object unit. The generated frames are queued for playback and displayed in reverse order. While the queue of frames is being displayed, frames from the preceding video object unit are generated and queued for display. A scaling algorithm can be utilized to reduce the amount of memory required for storage of a frame.
In yet another embodiment of the invention, an apparatus is provided that utilizes a memory to store a scaled version of a video frame in order to permit reverse playback of the video.
Another embodiment of the invention provides a system for playing a DVD video by playing the DVD in a slow reverse speed, pausing the DVD video and playing the DVD video in slow forward speed.
Other and further advantages and features of the invention will be apparent to those skilled in the art from a consideration of the following description taken in conjunction with the accompanying drawings wherein certain methods of and installations for practicing the invention are illustrated. However, it is to be understood that the invention is not limited to the details disclosed but includes all such variations and modifications as fall within the spirit of the invention and the scope of the appended claims.